Instruction manual
ACU-1000 Operations Manual
Interoperability Now 5-3
The HSP-2A includes voice prompt generator circuitry (U67, U24). The voice prompt
generator routes its prompt audio over one of the system audio buses via audio gates
U59 through U62.
The main function of the HSP-2A module is to connect 4-wire speaker and microphone
audio to the 16-line audio bus structure on the ACU main chassis backplane board.
Microphone audio is routed to the audio buses by audio gates U1 through U4, and
speaker audio is brought in from the audio buses by audio gates U5-U7, and U15. These
audio gates are controlled directly by audio bus latches U19 through U22, which receive
their instructions directly from the microprocessor on the HSP-2A.
The microprocessor, in turn, receives its instructions from the CPM-4 module in the system via
I/O latches and drivers U16 through U18. Thus, the connections to and from any audio bus are
controlled ultimately by the CPM-4 module, which decides which buses to assign to the HSP-
2A module depending on a number of system parameters. The CPM-4 passes connect
information to the microprocessor, which controls the audio gates.
Audio from an audio bus is routed to the speaker output through amplifier U10A, then through
speaker driver U11, where the output volume is set by pot R72. Monitor output audio is routed
to the back panel connector via amplifier U10B at a fixed zero dBm level. Microphone audio is
routed through preamp U12A, onto an audio bus through audio gates U1 through U4. A line-
level audio input is mixed into the input of U12A.
The /AuxO1, /AuxO2, and /AuxO3 digital outputs are generated by transistors Q1, Q2, and Q3
which are driven by the microprocessor. Digital inputs /AuxI1, /AuxI2, and /AuxI3 are routed
to gates U44C, U44D, and U44E, which are read by the microprocessor.
A keypad is interfaced to the microprocessor so the user can enter system commands and
programming parameters. The microprocessor then formats the keypad data and sends it to the
system’s CPM-4 for action.